Conventionally, image forming devices of an electrophotographic system, such as a printer, facsimile machine, photocopier, and multi function printer (MFP), form a toner image on a sheet by a photoreceptor drum and a transferring roller that is in contact with the photoreceptor drum. Further, the image forming devices heat and fuse the toner image on the sheet by a fusing unit that is configured with a heating roller and pressing roller that is pressed into contact with the heating roller. The sheet on which the toner image is formed by the fusing unit is carried to and stacked on a sheet discharge tray, which is located outside the image forming device.
In such a configuration, the size of the image forming device may be reduced by locating the fusing unit in the vicinity of and below the sheet discharging tray. Further, friction, which interferes with smooth movement of the discharged sheet, is reduced by forming multiple projections (or ribs) on an upper surface of a base of the sheet discharge tray. See Japanese laid-open patent publication No. 2006-053508.
However, in these conventional image forming devices, the fusing unit is close to the sheet discharging tray. Therefore, heat generated in the fusing unit tends to heat the sheet discharging tray. Consequently, sheets discharged on the sheet discharge tray may become attached each other by re-fusing of toner as a result of two types of heat. One is heat remaining in sheets just after the toner images are fused, and the other is heat that the sheet discharging tray maintains by itself.
The present application aims to resolve the deficit(s).